Re: vista..or XP?
Well...It all depends. I prefer XP myself, but I use almost all Windows versions daily. I have Win95 installed on my old Pentium 133 HTTP server, Win98SE installed on my Pentium MMX 200MHz (which I don't have a use for at the moment, the 40GB hard drive I was using in it for FTP died, and a 5GB FTP seems a bit lame). I had Win2k installed on my laptop and rebuilt Compaq, but upgraded both to XP recently, and I also have XP on my main desktop. My parents have Vista Home Premium on their PC.
I for one hate Vista, though it's a personal preference. I love the interface of it, yet it crashes on some of my old games, games that run perfectly fine under XP, 2000, and 98SE on all (but my old P200MMX, not powerful enough). I also despise User Account Control, the most annoying thing M$ ever thought of, which bugs you with a stupid message any time you try and run an administrative application (such as an installer, Windows config, or anything downloaded off the Internet). You can turn UAC off, but it can still bug you sometimes. My parents' comp is a Dell, they just bought it recently. One big turn-off of Vista is that out of the box, the computer had errors. Upon first boot, and ever since, it's given a message about an incompatible driver EVERY TIME YOU TURN IT ON! If it can't run the drivers that Dell picks for it (and they're experts, or so we'd hope), then it is truly hopeless.
Vista's also a mega-major resource hog. It's minimum req's are like a P3 850 or something...my friend had XP running on a hand-me-down Pentium 2 233MHz or so, and it ran perfectly well until it lagged down with a mega spyware jam from downloading too much stuff on P2P networks. XP runs well on my P3-850 laptop. Though Vista may include virus/spyware protection, if I seriously cared about viruses (right now, I care more about running my computer for less $$$, so I could care less...I can always reformat), I'd get McAfee or Norton or F-Secure or something known for being reliable, which work on both Vista and XP.
The only thing I can see that you would really want Vista for is games. New games. That's the only thing that really works, gaming wise, because old one's don't. If you're willing to spend $500 to have a DX10 compatible graphics card, you might as well use a DX10 compatible OS to play DX10 compatible games, else, use a DX9 compatible card, Windows XP, and play old (but good) games.